1. Field of the Invention
The present invention relates to a spindle motor for rotating a recording disk.
2. Description of the prior Art
In general, a spindle motor comprises a fitting member to be fitted to the frame of the spindle motor, a rotary member rotatably supported by the fitting member via a bearing member, a rotor magnet fitted to the inner surface of the rotary member and a stator fitted to the fitting member in such a manner that it confronts the rotor magnet. A recording disk such as a magnet disk is fitted to the rotary member. In spindle motors of a type whose shaft is fixed, a shaft member is secured to the fitting member, and the rotary member is rotatably fitted to the shaft member via the bearing member. In spindle motors of a type whose shaft rotates, a hollow cylindrical portion is formed in the fitting member and the shaft member is rotatably supported within this hollow cylindrical portion via the bearing member, the rotary member being secured to the thus supported shaft member.
However, in spindle motors of the type described above, the following problems to be overcome arise: since the bearing member is constituted by an inner and outer rings and a spherical member interposed between the inner and outer rings. Therefore, the size of the motor cannot be reduced due to the above-described structure of the bearing member. Furthermore, it is difficult to obtain a satisfactory accuracy in the rotation of the motor.
Furthermore, the spindle motor of the type described above employs a magnetic sealing mechanism or a labyrinth sealing mechanism for the purpose of protecting the surface of the recording disk from grease splashed from the bearing member. However, the employment of the magnetic sealing mechanism or the labyrinth sealing mechanism causes the overall structure of the motor to become too complicated and cost to be inevitably raised.